[FEATURE]: Desktop settings need a larger/resizable surface instead of a small modal with heavy scrolling

Problem

The Settings surface in OpenCode Desktop is a small modal window. Everything from general preferences to providers, models, and permissions lives inside this cramped area, so almost every section requires substantial scrolling, and wide content (keybind tables, provider configuration) gets squeezed.

For comparison, Codex presents its settings in a much larger dedicated surface where sections fit on screen without constant scrolling.

Proposal

Give the Desktop app a proper settings experience, e.g. one of:

• A full-size or user-resizable settings window
• Or a dedicated full-page settings view within the main window (sidebar navigation + content pane, like typical desktop app settings)
• Wider layouts for tabular sections (keybinds, providers) so rows don't wrap or truncate

This becomes more important as settings grow — permission management (#40909) and keybind customization are active requests, and both need room.

Related reports

• #34108 — scrolling entirely broken in the Provider/Model settings panels on Windows
• #41726 — cannot scroll down in the provider list

Those bugs make the small-modal layout worse today; but even when scrolling works, the surface itself is too small for comfortable use.

Environment

• App: OpenCode Desktop 1.18.21
• OS: Microsoft Windows 11 Education, 25H2, build 26200.8875